National Council of Educational Research and Training (NCERT) Book for Class XI
Subject: Economics
Chapter: Chapter 9 – Environment and Sustainable Development

Class XI NCERT Economics Text Book Chapter 9 Environment and Sustainable Development is given below.

After studying this chapter, the learners will

understand the concept of environment

analyse the causes and effects of ‘environmental degradation’ and ‘resource depletion’

understand the nature of environmental challenges facing India

relate environmental issues to the larger context of sustainable development.

9.1 INTRODUCTION

In the earlier chapters we havediscussed the main economic issuesfaced by the Indian economy. Theeconomic development that we haveachieved so far has come at a very heavyprice—at the cost of environmentalquality. As we step into an era ofglobalisation that promises highereconomic growth, we have to bear inmind the adverse consequences of thepast development path on ourenvironment and consciously choose apath of sustainable development. Tounderstand the unsustainable path ofdevelopment that we have taken andthe challenges of sustainabledevelopment, we have to firstunderstand the significance andcontribution of environment toeconomic development. With this inmind, this chapter is divided into threesections. The first part deals with thefunctions and role of environment. Thesecond section discusses the state ofIndia’s environment and the thirdsection deals with steps and strategiesto achieve sustainable development.

9.2 ENVIRONMENT — DEFINITION ANDFUNCTIONS

Environment is defined as the totalplanetary inheritance and the totalityof all resources. It includes all the biotic and abiotic factors that influence eachother. While all living elements—thebirds, animals and plants, forests,fisheries etc.—are biotic elements,abiotic elements include air, water, landetc. Rocks and sunlight are allexamples of abiotic elements of theenvironment. A study of the environmentthen calls for a study of the interrelationshipbetween these biotic andabiotic components of the environment.

Functions of the Environment: Theenvironment performs four vitalfunctions (i) it supplies resources:resources here include both renewableand non-renewable resources.Renewable resources are those whichcan be used without the possibility ofthe resource becoming depleted orexhausted. That is, a continuoussupply of the resource remainsavailable. Examples of renewableresources are the trees in the forests andthe fishes in the ocean. Non-renewableresources, on the other hand, are thosewhich get exhausted with extractionand use, for example, fossil fuel (ii) itassimilates waste (iii) it sustains life byproviding genetic and bio diversity and(iv) it also provides aesthetic serviceslike scenery etc.

The environment is able to performthese functions without any interruptionas long as the demand on these

functions is within its carryingcapacity. This implies that the resourceextraction is not above the rate ofregeneration of the resource and thewastes generated are within theassimilating capacity of theenvironment. When this is not so, theenvironment fails to perform its thirdand vital function of life sustenance and

this results in anenvironmental crisis. Thisis the situation todayall over the world. Therising population of thedeveloping countries andthe affluent consumptionand production standardsof the developed world haveplaced a huge stress on theenvironment in terms of itsfirst two functions. Manyresources have becomeextinct and the wastesgenerated are beyond the absorptive capacity of theenvironment. Absorptivecapacity means the abilityof the environment toabsorb degradation. The result — weare today at the threshold ofenvironmental crisis. The pastdevelopment has polluted and dried uprivers and other aquifers making wateran economic good. Besides, theintensive and extensive extraction ofboth renewable and non-renewableresources has exhausted some of these

Box 9.1: Global Warming

Global warming is a gradual increase in the average temperature of the earth’slower atmosphere as a result of the increase in greenhouse gases since theIndustrial Revolution. Much of the recent observed and projected globalwarming is human-induced. It is caused by man-made increases in carbondioxide and other greenhouse gases through the burning of fossil fuels anddeforestation. Adding carbon dioxide, methane and such other gases (thathave the potential to absorb heat) to the atmosphere with no other changeswill make our planet’s surface warmer. The atmospheric concentrations ofcarbon dioxide and CH4 have increased by 31 per cent and 149 per centrespectively above pre-industrial levels since 1750. During the past century,the atmospheric temperature has risen by 1.1°F (0.6°C) and sea level hasrisen several inches. Some of the longer-term results of global warming aremelting of polar ice with a resulting rise in sea level and coastal flooding;disruption of drinking water supplies dependent on snow melts; extinction ofspecies as ecological niches disappear; more frequent tropical storms; and anincreased incidence of tropical diseases.Among factors that may be contributing to global warming are the burningof coal and petroleum products (sources of carbon dioxide, methane, nitrousoxide, ozone); deforestation, which increases the amount of carbon dioxide inthe atmosphere; methane gas released in animal waste; and increased cattleproduction, which contributes to deforestation, methane production, and useof fossil fuels. A UN Conference on Climate Change, held in Kyoto, Japan, in1997, resulted in an international agreement to fight global warming whichcalled for reductions in emissions of greenhouse gases by industrialised nations.Source: www.wikipedia.org

vital resources and we are compelledto spend huge amounts on technologyand research to explore new resources.Added to these are the health costs ofdegraded environmental quality —decline in air and water quality (seventyper cent of water in India is polluted)have resulted in increased incidence ofrespiratory and water-borne diseases.Hence the expenditure on health is alsorising. To make matters worse, globalenvironmental issues such as globalwarming and ozone depletion alsocontribute to increased financialcommitments for the government.

Thus, it is clear that the opportunitycosts of negative environmentalimpacts are high.

The biggest question that arises is:are environmental problems new to thiscentury? If so, why? The answer to thisquestion requires some elaboration. Inthe early days when civilisation justbegan, or before this phenomenalincrease in population, and beforecountries took to industrialisation, thedemand for environmental resourcesand services was much less than theirsupply. This meant that pollution waswithin the absorptive capacity of the

Box 9.2: Ozone Depletion

Ozone depletion refers to the phenomenon of reductions in the amount of ozonein the stratosphere. The problem of ozone depletion is caused by high levelsof chlorine and bromine compounds in the stratosphere. The origins of thesecompounds are chlorofluorocarbons (CFC), used as cooling substances in airconditionersand refrigerators, or as aerosol propellants, and bromofluorocarbons (halons), used in fire extinguishers. As a result of depletionof the ozone layer, more ultraviolet (UV) radiation comes to Earth and causesdamage to living organisms. UV radiation seems responsible for skin cancerin humans; it also lowers production of phytoplankton and thus affects otheraquatic organisms. It can also influence the growth of terrestrial plants. Areduction of approximately 5 per cent in the ozone layer was detected from1979 to 1990. Since the ozone layer prevents most harmful wavelengths ofultraviolet light from passing through the Earth’s atmosphere, observed andprojected decreases in ozone have generated worldwide concern. This led tothe adoption of the Montreal Protocol banning the use of chlorofluorocarbon(CFC) compounds, as well as other ozone depleting chemicals such as carbontetrachloride, trichloroethane (also known as methyl chloroform), and brominecompounds known as halons.

Source: www.ceu.hu

environment and the rate of resource extraction was less than the rate of regeneration of these resources. Hence environmental problems did not arise.

But with population explosion and withthe advent of industrial revolutionto meet the growing needs of theexpanding population, thingschanged. The result was that thedemand for resources for bothproduction and consumptionwent beyond the rate ofregeneration of the resources; thepressure on the absorptivecapacity of the environmentincreased tremendously — thistrend continues even today. Thuswhat has happened is a reversalof supply-demand relationshipfor environmental quality — weare now faced with increaseddemand for environmentalresources and services but theirsupply is limited due to overuse

India has abundantnatural resources interms of rich qualityof soil, hundreds ofrivers and tributaries,lush green forests,plenty of mineraldeposits beneath the land surface, vaststretch of the Indian Ocean, ranges ofmountains, etc. The black soil of theDeccan Plateau is particularly suitablefor cultivation of cotton, leading toconcentration of textile industries in thisregion. The Indo-Gangetic plains —spread from the Arabian Sea to the Bayof Bengal — are one of the most fertile,intensively cultivated and denselypopulated regions in the world. India’sforests, though unevenly distributed,provide green cover for a majority of itspopulation and natural cover for itswildlife. Large deposits of iron-ore, coaland natural gas are found in thecountry. India alone accounts fornearly 20 per cent of the world’s totaliron-ore reserves. Bauxite, copper,chromate, diamonds, gold, lead, lignite,manganese, zinc, uranium, etc. are alsoavailable in different parts of thecountry. However, the developmentalactivities in India have resulted in

pressure on its finite naturalresources, besides creating impacts onhuman health and well-being. Thethreat to India’s environment poses adichotomy—threat of poverty-inducedenvironmental degradation and, at thesame time, threat of pollution fromaffluence and a rapidly growingindustrial sector. Air pollution,water contamination, soil erosion,deforestation and wildlife extinctionare some of the most pressingenvironmental concerns of India. Thepriority issues identified are (i) landdegradation (ii) biodiversity loss (iii) airpollution with special reference tovehicular pollution in urban cities (iv)management of fresh water and (v) solidwaste management. Land in Indiasuffers from varying degrees and typesof degradation stemming mainly fromunstable use and inappropriatemanagement practices.

Box. 9.3: Chipko or Appiko — What’s in a Name?

You may be aware of the Chipko Movement, which aimed at protecting forestsin the Himalayas. In Karnataka, a similar movement took a different name,‘Appiko’, which means to hug. On 8 September 1983, when the felling of treeswas started in Salkani forest in Sirsidistrict, 160 men, women and childrenhugged the trees and forced thewoodcutters to leave. They kept vigil inthe forest over the next six weeks. Onlyafter the forest officials assured thevolunteers that the trees will be cutscientifically and in accordance with theworking plan of the district, did theyleave the trees.

When commercial felling bycontractors damaged a large number ofnatural forests, the idea of hugging thetrees gave the people hope andconfidence that they can protect theforests. On that particular incident, withthe felling discontinued, the people saved12,000 trees. Within months, thismovement spread to many adjoiningdistricts.

Indiscriminate felling of trees for fuelwood and for industrial use has led to many environmental problems.Twelve years after setting up of a paper mill in Uttar Kanara area, bamboohas been wiped out from that area. “Broad-leaved trees which protected thesoil from the direct onslaught of rain have been removed, the soil washedaway, and bare laterite soil left behind. Now nothing grows but a weed”, saysa farmer. Farmers also complain that rivers and rivulets dry up quicker, andthat rainfall is becoming erratic. Diseases and insects earlier unknown arenow attacking the crops.

Appiko volunteers want the contractors and forest officials to follow certainrules and restrictions. For instance, local people should be consulted whentrees are marked for felling and trees within 100 metres of a water sourceand on a slope of 30 degrees or above should not be felled.Do you know that the government allocates forestlands to industries touse forest materials as industrial raw material? Even if a paper mill employs10,000 workers and a plywood factory employs 800 people but if they deprivethe daily needs of a million people, is it acceptable? What do you think?Source: Excerpts from ‘State of India’s Environment 2: The Second Citizens’ Report 1984-85’,Centre for Science and Environment, 1996, New Delhi.

Some of the factors responsiblefor land degradation are (i) lossof vegetation occuring due todeforestation (ii) unsustainable fuelwood and fodder extraction (iii) shiftingcultivation (iv) encroachment into forestlands (v) forest fires and over grazing(vi) non-adoption of adequate soilconservation measures (vii) impropercrop rotation (viii) indiscriminate use ofagro-chemicals such as fertilisers andpesticides (ix) improper planning andmanagement of irrigation systems(x) extraction of ground water in

the competing uses of land forforestry, agriculture, pastures, humansettlements and industries exert anenormous pressure on the country’sfinite land resources.The per capita forestland in thecountry is only 0.08 hectare againstthe requirement of 0.47 hectare to meetbasic needs, resulting in an excessfelling of about 15 million cubic metreforests over the permissible limit.Estimates of soil erosion show thatsoil is being eroded at a rate of 5.3billion tonnes a year for the entire

excess of the recharge capacity (xi)open access resource and (xii) povertyof the agriculture-dependent people.India supports approximately 16per cent of the world’s human and 20per cent of livestock population on amere 2.5 per cent of the world’sgeographical area. The high densityof population and livestock and

country as a result of which thecountry loses 0.8 million tonnes ofnitrogen, 1.8 million tonnes ofphosphorus and 26.3 million tonnesof potassium every year. According tothe Government of India, the quantityof nutrients lost due to erosion eachyear ranges from 5.8 to 8.4 milliontonnes.

Box 9.4 : Pollution Control Boards

In order to address two major environmental concerns in India, viz., waterand air pollution, the government set up the Central Pollution Control Board(CPCB) in 1974. This was followed by states establishing their own state levelboards to address all the environmental concerns. They investigate, collectand disseminate information relating to water, air and land pollution, lay downstandards for sewage/trade effluent and emissions. These boards providetechnical assistance to governments in promoting cleanliness of streams andwells by prevention, control and abatement of water pollution, and improvethe quality of air and to prevent, control or abate air pollution in the country.These boards also carry out and sponsor investigation and researchrelating to problems of water and air pollution and for their prevention, controlor abatement. They also organise, through mass media, a comprehensive massawareness programme for the same. They also prepare manuals, codes andguidelines relating to treatment and disposal of sewage and trade effluents.They assess the air quality through regulation of industries. In fact, stateboards, through their district level officials, periodically inspect every industryunder their jurisdiction to assess the adequacy of treatment measures providedto treat the effluent and gaseous emissions. It also provides background airquality data needed for industrial siting and town planning.The pollution control boards collect, collate and disseminate technical andstatistical data relating to water pollution. They monitor the quality of waterin 125 rivers (including the tributaries), wells, lakes, creeks, ponds, tanks,
drains and canals.

Visit a nearby factory/irrigation department and collect the details ofmeasures that they adopt to control water and air pollution.

You might be seeing advertisements in newspapers, radio and televisionor billboards in your locality on awareness programmes relating to waterand air pollution. Collect a few news-clippings, pamphlets and otherinformation and discuss them in the classroom.

In India, air pollution is widespreadin urban areas where vehicles are themajor contributors and in a few otherareas which have a high concentrationof industries and thermal power plants.Vehicular emissions are of particularconcern since these are ground levelsources and, thus, have the maximumimpact on the general population. Thenumber of motor vehicles has increasedfrom about 3 lakh in 1951 to 67 croresin 2003. In 2003, personal transport vehicles (two-wheeled vehicles and carsonly) constituted about 80 per cent ofthe total number of registered vehiclesthus contributing significantly to totalair pollution load.

India is one of the ten mostindustrialised nations of the world.But this status has brought withit unwanted and unanticipatedconsequences such as unplannedurbanisation, pollution and the risk ofaccidents. The CPCB (Central Pollution Control Board) has identified seventeencategories of industries (largeand medium scale) as significantlypolluting.

The above points highlight thechallenges to India’s environment. Thevarious measures adopted by theMinistry of Environment and thecentral and state pollution controlboards may not yield reward unlesswe consciously adopt a path ofsustainable development. The concernfor future generations alone can makedevelopment last forever. Developmentto enhance our current living styles,without concern for posterity, willdeplete resources and degradeenvironment at a pace that is bound toresult in both environmental andeconomic crisis.

9.4. SUSTAINABLE DEVELOPMENT

Environment and economy areinterdependent and need each other.Hence, development that ignores itsrepercussions on the environment willdestroy the environment that sustainslife forms. What is needed is sustainabledevelopment: development that will

allow all future generations to have apotential average quality of life that isat least as high as that which is beingenjoyed by the current generation. Theconcept of sustainable developmentwas emphasised by the United NationsConference on Environment andDevelopment (UNCED), which definedit as: ‘Development that meets the needof the present generation withoutcompromising the ability of the futuregeneration to meet their own needs’.Read the definition again. You willnotice that the term ‘need’ and thephrase ‘future generations’ in thedefinition are the catch phrases. Theuse of the concept ‘needs’ in thedefinition is linked to distribution ofresources. The seminal report—OurCommon Future—that gave the abovedefinition explained sustainabledevelopment as ‘meeting the basicneeds of all and extending to all theopportunity to satisfy their aspirationsfor a better life’. Meeting the needs ofall requires redistributing resourcesand is hence a moral issue.Edward Barbier defined sustainabledevelopment as one which is directlyconcerned with increasing the materialstandard of living of the poor atthe grass root level — this can bequantitatively measured in terms ofincreased income, real income,educational services, health care,sanitation, water supply etc. In morespecific terms, sustainable developmentaims at decreasing the absolute povertyof the poor by providing lasting andsecure livelihoods that minimiseresource depletion, environmental degradation, cultural disruption andsocial instability. Sustainabledevelopment is, in this sense, adevelopment that meets the basic needsof all, particularly the poor majority, foremployment, food, energy, water,housing, and ensures growth ofagriculture, manufacturing, power andservices to meet these needs.

The Brundtland Commissionemphasises on protecting the futuregeneration. This is in line with theargument of the environmentalists whoemphasise that we have a moralobligation to hand over the planet earthin good order to the future generation;that is, the present generation shouldbequeath a better environment to thefuture generation. At least we shouldleave to the next generation a stock of‘quality of life’ assets no less than whatwe have inherited.

The present generation shouldpromote development that enhancesthe natural and built environment inways that are compatible with

(i) conservation of natural assets

(ii) preservation of the regenerativecapacity of the world’s naturalecological system

According to Herman Daly, a leadingenvironmental economist, to achievesustainable development, the followingneeds to be done (i) limiting the humanpopulation to a level within the carryingcapacity of the environment. The carryingcapacity of the environment is like a ‘plimsoll line’ of the ship which is its loadlimit mark. In the absence of the plimsoll

line for the economy, human scale growsbeyond the carrying capacity of the earthand deviates from sustainabledevelopment (ii) technological progressshould be input efficient and not input consuming (iii) renewable resourcesshould be extracted on a sustainablebasis, that is, rate of extraction shouldnot exceed rate of regeneration (iv) fornon-renewable resources rate of depletionshould not exceed the rate of creationof renewable substitutes and(v) inefficiencies arising from pollutionshould be corrected.

9.5 STRATEGIES FOR SUSTAINABLEDEVELOPMENT

Use of Non-conventional Sources ofEnergy: India, as you know, is hugelydependent on thermal and hydropower plants to meet its powerneeds. Both of these have adverseenvironmental impacts. Thermalpower plants emit large quantities ofcarbon dioxide which is a green housegas. It also produces fly ash which, ifnot used properly, can cause pollutionof water bodies, land and othercomponents of the environment.Hydroelectric projects inundate forestsand interfere with the natural flow ofwater in catchment areas and the riverbasins. Wind power and solar rays aregood examples of conventional butcleaner and greener technologies whichcan be effectively used to replacethermal and hydro-power.

LPG, Gobar Gas in Rural Areas:Households in rural areas generally usewood, dung cake or other biomass as fuel. This practice has several adverseimplications like deforestation,reduction in green cover, wastage ofcattle dung and air pollution. To rectifythe situation, subsidised LPG is beingprovided. In addition, gobar gas plantsare being provided through easy loansand subsidy. As far as liquefiedpetroleum gas (LPG) is concerned, it isa clean fuel — it reduces householdpollution to a large extent. Also, energywastage is minimised. For the gobargas plant to function, cattle dung is fedto the plant and gas is produced whichis used as fuel while the slurry whichis left over is a very good organicfertiliser and soil conditioner.

CNG in Urban Areas: In Delhi, the use ofCompressed Natural Gas (CNG) as fuel inpublic transport system has significantlylowered air pollution and the air hasbecome cleaner in the last few years.

Wind Power: In areas where speed ofwind is usually high, wind mills canprovide electricity without any adverseimpact on the environment. Windturbines move with the wind andelectricity is generated. No doubt, theinitial cost is high. But the benefits aresuch that the high cost gets easilyabsorbed.

Solar Power through PhotovoltaicCells: India is naturally endowed witha large quantity of solar energy in theform of sunlight. We use it in differentways. For example, we dry our clothes,grains, other agricultural products aswell as various items made for daily use.We also use sunlight to warm ourselvesin winter. Plants use solar energy toperform photosynthesis. Now, with thehelp of photovoltaic cells, solar energycan be converted into electricity. Thesecells use special kind of materials tocapture solar energy and then convertthe energy into electricity. Thistechnology is extremely useful for remoteareas and for places where supply ofpower through grid or power lines iseither not possible or proves very costly.This technique is also totally free frompollution.

Mini-hydel Plants: In mountainousregions, streams can be found almosteverywhere. A large percentage of suchstreams are perennial. Mini-hydelplants use the energy of such streamsto move small turbines. The turbinesgenerate electricity which can be usedlocally. Such power plants are more orless environment-friendly as they do notchange the land use pattern in areaswhere they are located; they generateenough power to meet local demands.This means that they can also do awaywith the need for large scaletransmission towers and cables andavoid transmission loss.

Traditional Knowledge and Practices: Traditionally, Indian peoplehave been close to their environment. They have been more a component ofthe environment and not its controller.If we look back at our agriculturesystem, healthcare system, housing,transport etc., we find that all practiceshave been environment friendly. Onlyrecently have we drifted away from thetraditional systems and caused largescale damage to the environment andalso our rural heritage. Now, it is timeto go back. One apt example is inhealthcare. India is very muchprivileged to have about 15,000 speciesof plants which have medicinalproperties. About 8,000 of these are inregular use in various systems oftreatment including the folk tradition.With the sudden onslaught of thewestern system of treatment, we wereignoring our traditional systems suchas Ayurveda, Unani, Tibetan and folksystems. These healthcare systems arein great demand again for treatingchromic health problems. Now a daysevery cosmetic produce — hair oil,toothpaste, body lotion, face cream andwhat not — is herbal in composition.Not only are these products environmentfriendly, they are relatively free from sideeffects and do not involve large-scaleindustrial and chemical processing

.Biocomposting: In our quest toincrease agricultural productionduring the last five decades or so, wealmost totally neglected the use ofcompost and completely switched overto chemical fertilisers. The result is thatlarge tracts of productive land havebeen adversely affected, water bodiesincluding ground water system havesuffered due to chemical contamination and demand for irrigation has beengoing up year after year.

Farmers, in large numbers all overthe country, have again started usingcompost made from organic wastes ofdifferent types. In certain parts of thecountry, cattle are maintained onlybecause they produce dung which isan important fertiliser and soilconditioner.

Earthworms can convert organicmatter into compost faster than thenormal composting process. Thisprocess is now being widely used.Indirectly, the civic authorities arebenefited too as they have to disposereduced quantity of waste.

Biopest Control: With the advent ofgreen revolution, the entire countryentered into a frenzy to use more andmore chemical pesticides for higheryield. Soon, the adverse impacts beganto show; food products werecontaminated, soil, water bodies andeven ground water were polluted withpesticides. Even milk, meat and fisheswere found to be contaminated.

To meet this challenge, efforts areon to bring in better methods of pestcontrol. One such step is the use ofpesticides based on plant products.Neem trees are proving to be quiteuseful. Several types of pest controllingchemicals have been isolated from neemand these are being used. Mixedcropping and growing different cropsin consecutive years on the same landhave also helped farmers.

In addition, awareness is spreadingabout various animals and birds which help in controlling pests. For example,snakes are one of the prime group ofanimals which prey upon rats, mice andvarious other pests. Similarly, largevarieties of birds, for example, owls andpeacocks, prey upon vermin and pests.If these are allowed to dwell around theagricultural areas, they can clear largevarieties of pests including insects.Lizards are also important in thisregard. We need to know their value andsave them.

Sustainable development hasbecome a catch phrase today. It is‘indeed’ a paradigm shift indevelopment thinking. Though it hasbeen interpreted in a number of ways,adherence to this path ensures lastingdevelopment and non-declining welfarefor all.

9.6 CONCLUSION

Economic development, which aimed atincreasing the production of goods andservices to meet the needs of a risingpopulation, puts greater pressure onthe environment. In the initial stagesof development, the demand forenvironmental resources was less thanthat of supply. Now the world isfaced with increased demand forenvironmental resources but theirsupply is limited due to overuse andmisuse. Sustainable development aimsat promoting the kind of developmentthat minimises environmental problemsand meets the needs of the presentgeneration without compromising theability of the future generation to meettheir own needs.

1. What is meant by environment?

2. What happens when the rate of resource extraction exceeds that oftheir regeneration?

16. Highlight any two serious adverse environmental consequences ofdevelopment in India. India’s environmental problems pose a dichotomy— they are poverty induced and, at the same time, due to affluence inliving standards—is this true?

17. What is sustainable development?

18. Keeping in view your locality, describe any four strategies of sustainabledevelopment.

19. Explain the relevance of intergenerational equity in the definition ofsustainable development.

1. Suppose 70 lakh cars are added every year to the roads of metropolitans.Which type of resources do you think are undergoing depletion? Discuss.

2. Make a list of items that can be recycled.

3. Prepare a chart on the causes and remedies of soil erosion in India.

4. How does population explosion contribute to the environmental crisis?Debate in the classroom.

5. The nation has to pay heavily for correcting environmental damages—discuss.

6. A paper factory is to be set up in your village. Arrange a role playconsisting of an activist, an industrialist and a group of villagers.